The present invention relates generally to photolithographic mask fabrication, and specifically to a method of extreme ultraviolet mask engineering.
Extreme ultraviolet is the most commonly accepted solution for next generation lithography (NGL). The mask is a reflective system having up to 50 pairs of multi-layer materials and the absorber layer patterned with low temperature processes. The current two basic EUV mask patterning approaches (Direct Metal Patterning and Damascene Process) involves multi-steps of etching/film deposition/chemical mechanical polishing (CMP) process.
U.S. Pat. No. 5,958,629 to Yan et al. describes a method of fabricating EUV masks by forming an etch stop layer over the surface of a mask to create a more controllable etch profile for etching patterns into the material above the etch stop layer.
U.S. Pat. No. 5,935,737 to Yan describes a method of fabricating EUV masks using dual defect-absorbing layers to ensure that through two steps of repair, the repair stains are eliminated on that section of the mask which must cleanly reflect light in the case of a reflective mask, or transmit light in the case of a transmissive mask.
U.S. Pat. No. 5,521,031 to Tenant et al. describes a method of fabricating EUV masks by incorporating the operating principle of the attenuated phase mask in a reflecting structure. The apparatus serves as an alternative, or supplement, to a surface-activated resist to permit projection-reduction lithography with improved image edge definition.
Accordingly, it is an object of the present invention to provide EUV masks and a method of fabricating the EUV masks using less processing steps.
Another object of the present invention is to provide EUV masks and a method of fabricating the EUV masks using low processing temperatures.
Yet another object of the present invention is to provide EUV masks and a method of fabricating the EUV masks with minimum sub-layer damage.
A further object of the present invention is to provide an easier and more economic method of fabricating EUV masks.
Another object of the present invention is to use nickel (Ni) as an absorber layer instead of chromium (Cr) allowing for a relatively low temperature etch.
Other objects will appear hereinafter.
It has now been discovered that the above and other objects of the present invention may be accomplished in the following manner. The EUV photolithographic mask comprises a multi-layer over an EUV masking substrate and a patterned light absorbing layer formed on the multi-layer. The method comprises the steps of forming a multi-layer on an EUV mask substrate, forming a light absorbing layer on the multi-layer, and etching an opening through the light absorbing layer to the multi-layer. The light absorbing layer includes a metal selected from the group comprising nickel, chromium and cobalt and is preferably nickel.